VPN with conflicting subnets with Netscreen-50 and ZyWALL 70

Hello,

I've been trying to setup a VPN between our LAN office and a client's LAN. The problem being that we have conflicting subnets : more specifically, I want to access the 192.168.0.0/24 and 192.168.1.0/24 subnets of our client, and since we already use these adresses, I would like to map them to 10.0.5.0/24 and 10.0.6.0/24.

We want to access the client's subnets for monitoring purposes, and we don't need the client to be able to access our subnet however.

I've been reading the reference guide of Netscreen on VPNs, but have had problems understanding the various concepts so far. It seems to me I need to configure things such as MIP/DIP on both ends of the VPN tunnel; however I'm not entirely sure about it, given that the client doesn't need to access our LAN.

Our equipment is a NetScreen-50, however the client uses a ZyXel ZyWALL

70, and I'm not sure (once again!) that it has the functionality to play nice with the Netscreen on this problem.

Would it be possible to solve this by only using MIP/DIP on the Netscreen device or have I no choice but to try to configure something similar on the client's device? Can someone confirm or infirm that the ZyXel device also has MIP/DIP or an equivalent functionality (assuming I need it)?

Thanks in advance for the help.

Cheers, Maxime Henrion